ATX Power Supply Units Roundup. Part X. Page 10

This article is our report about five power supplies from well-known brands ranging from 500W to 800W . Two companies, namely Thermaltake and Enermax, are long known as PSU makers, but the other three are new names in the market of power supplies.

There is a 400V/390µF capacitor from Hitachi at the PSU’s input. Samxon’s capacitors are installed at the output.

Of course, the most exciting part of this PSU is its fan. It is an Everflow R121225BL with a standard form-factor of 120x120x25mm and a rated speed of 2000rpm.

The fan is in fact case-less. The motor and impeller are fastened to a frame that doesn’t have side panels. There are only four poles for self-tipping screws that fix the fan within the PSU case.

As I wrote above, there are horizontal slits around the case. You can see the fan’s impeller through them.

According to Thermaltake (the picture above is taken from the company’s website), the fan takes the air in through those slits, thus increasing the cooling efficiency.

Well, but I think that when a fan is rotating, the centrifugal force makes the air move outward and not in some other way. This is the operating principle of blowers that are often employed to cool graphics cards: their impeller is driving the air away from the rotation axis rather than along it.

Then, it is also clear that a high-pressure zone is developed under the fan’s impeller when the fan is rotating. And of course, the outside air can’t be forced in there. The air can only move out of there to the outside!

So who is wrong about these basic things, me or Thermaltake? I performed a small experiment by placing a piece of paper on a side panel of the operating PSU:

It is clear that the paper goes off the PSU rather than clings to it. It means that the air is going out of the slits but not into them. Alas, the picture at the Thermaltake website is quite misleading.

As a matter of fact, I wanted to make a snapshot of a burning match. This is a standard way of identifying weak airflows. But the airflow coming out of the QFan is not weak. It just blew the fire off the match!

The noise properties of the QFan will be discussed shortly. Right now I’ll continue to describe the PSU.

It is equipped with the following cables and connectors:

Mainboard cable with a 20+4-pin connector (48cm long)

CPU cable with an 8-pin connector (49cm)

Four connectors for power cables of hard and optical drives

Two connectors for graphics card cables

One connector for a CPU power cable

Included with the power supply are:

CPU cable with 8-pin and 4-pin connectors (49+15cm)

Two graphics card cables with 6-pin connectors (49cm)

Two SATA power cables with three connectors on each (49+15+15cm)

One cable with three Molex connectors and one floppy-drive plug (49+15+15+15cm)

One cable with four Molex connectors and one floppy-drive plug (49+15+15+15+15cm)

So, this is a good selection of cables but you’ll have to use an adapter for the fourth graphics card connector if you are assembling a SLI/CrossFire graphics subsystem. Moreover, two CPU power connectors are only necessary for a few advanced mainboards targeted at servers and workstations. In most computers the extra connector on the appropriate cable will just be a nuisance. It would be handier if the kit included two different cables, one with an 8-pin and the other with a 4-pin connector.